Biomedical subjects

L M De Luca

Publications and source records attributed to L M De Luca.

At least 37 records · Page 2Linked to original sources

PubMed1999

Retinoic acid and 4-hydroxyphenylretinamide induce growth inhibition and tissue transglutaminase through different signal transduction pathways in mouse fibroblasts (NIH 3T3 cells).

4-Hydroxyphenylretinamide (4-HPR) is a synthetic retinoid with minimal toxicity and favorable pharmacokinetics during long-term administration to patients in clinical trials. Since 4-HPR binds poorly to the retinoic acid receptors, the issue of whether 4-HPR exerts its biological actions via classical retinoid receptor pathways remains to be resolved. We have previously reported that stable expression of a truncated retinoic acid receptor alpha, RARalpha403, transduced in NIH 3T3 cells by a retroviral vector, rendered the cells resistant to retinoic acid for growth inhibition and induction of tissue transglutaminase (TGase II). Here, we report that stable expression of the dominant negative construct RARalpha403 fails to blunt growth inhibition and TGase II induction by 4-HPR, a potent chemopreventive retinoid, in the same cells. These data show that retinoic acid receptors do not mediate either growth inhibition or induction of TGase II activity by 4-HPR in mouse fibroblast cells.

3T3 Cells↗

PubMed1999

Vitamin A-sensitive tissues in transgenic mice expressing high levels of human cellular retinol-binding protein type I are not altered phenotypically.

The suggested function of cellular retinol-binding protein type I [CRBP(I)] is to carry retinol to esterifying or oxidizing enzymes. The retinyl esters are used in storage or transport, whereas oxidized forms such as all-trans or 9-cis retinoic acid are metabolites used in the mechanism of action of vitamin A. Thus, high expression of human CRBP(I) [hCRBP(I)] in transgenic mice might be expected to increase the production of retinoic acid in tissues, thereby inducing a phenotype resembling vitamin A toxicity. Alternatively, a vitamin A-deficient phenotype could also be envisioned as a result of an increased accumulation of vitamin A in storage cells induced by a high hCRBP(I) level. Signs of vitamin A toxicity or deficiency were therefore examined in tissues from transgenic mice with ectopic expression of hCRBP(I). Testis and intestine, the tissues with the highest expression of the transgene, showed normal gross morphology. Similarly, no abnormalities were observed in other tissues known to be sensitive to vitamin A status such as cornea and retina, and the epithelia in the cervix, trachea and skin. Furthermore, hematologic variables known to be influenced by vitamin A status such as the hemoglobin concentration, hematocrits and the number of red blood cells were within normal ranges in the transgenic mice. In conclusion, these transgenic mice have normal function of vitamin A despite high expression of hCRBP(I) in several tissues.

Animals↗

PubMed1998

Topical retinoic acid reduces skin papilloma formation but resistant papillomas are at high risk for malignant conversion.

Retinoic acid (RA) was topically applied to the skin of Sencar mice during the promotion phase of specific tumor induction protocols that produce papillomas at low (12-O-tetradecanoylphorbol-13-acetate promoted, TPA) or high (mezerein-promoted) risk for premalignant progression and malignant conversion. RA consistently reduced the yield of papillomas and carcinomas in both protocols, but the frequency of malignant conversion in papillomas that emerged during RA treatment was not reduced. When TPA was reapplied after cessation of RA treatment, the number of papillomas increased 2-fold, suggesting that RA had not eliminated initiated cells. In vitro, RA prevented the emergence of transformed keratinocytes in an assay that mimics malignant conversion, suggesting that RA can suppress conversion if applied during the stage of premalignant progression. Examination of tumor markers at weeks 14 and 22 of the tumor-induction experiments in vivo indicated that papillomas evolving during RA treatment exhibited a phenotype of high progression risk, even in the TPA-promoted groups. In the majority of these tumors, the alpha6beta4 integrin and retinoid X receptor alpha transcripts were detected suprabasally, indicating an advanced state of premalignant progression. RA-treated tumors also expressed higher levels of transcripts for transforming growth factor (TGF)-beta1 and localized TGF-beta1 peptide in the basal portions of the tumor fronds. Because up-regulated expression of TGF-beta1 suppresses papilloma formation, these studies suggest a mechanism whereby RA can prevent papilloma eruption via a TGF-beta intermediate, but papillomas resistant to RA may have altered TGF-beta signaling and progress to carcinomas at an increased frequency.

Administration, Topical↗

PubMed1997

Expression of a dominant-negative retinoic acid receptor construct reduces retinoic acid metabolism and retinoic acid-induced inhibition of NIH-3T3 cell growth.

We have previously reported an unexpected relationship between retinoic acid-induced inhibition of cell growth and the ability of various cell lines to metabolize the retinoid. Here, we report that stable expression of the truncated retinoic acid receptor RAR alpha403, transduced in NIH-3T3 cells by a retroviral vector, rendered the cells resistant to retinoic acid for growth inhibition and reduced their ability to metabolize the retinoid at the same time as it blunted the induction of the target gene transglutaminase II. The data suggest that retinoic acid receptors mediate the growth-inhibitory action of retinoic acid as well as its metabolism and the induction of transglutaminase II.

3T3 Cells↗

PubMed1997

Decreased retinoylation in NIH 3T3 cells transformed with activated Ha-ras.

Retinoylation (retinoic acid acylation) is a post-translation modification of proteins occurring in a variety of mammalian cell lines and in vivo. To gain further knowledge of the role of retinoylation we studied it in NIH 3T3 cells and NIH 3T3 cells transformed by an activated Ha-ras oncogene (NIH Ha-ras-3T3 cells). In serum-free medium retinoic acid (RA) inhibited growth of NIH 3T3 cells but did not inhibit growth of NIH Ha-ras-3T3 cells. After incubation with [3H]RA, the level of retinoylated protein in NIH 3T3 cells was about 1.5-fold greater than in NIH Ha-ras-3T3 cells. On one-dimensional polyacrylamide gel electrophoresis, both the rate and the extent of retinoylation were greater in NIH 3T3 cells. We detected about 40 retinoylated proteins in NIH 3T3 cells by two-dimensional polyacrylamide gel electrophoresis. Only about 15 proteins were retinoylated, but at reduced levels, in NIH Ha-ras-3T3 cells. These results suggest that the activated ras oncogene inhibits retinoylation. This inhibition may in turn be related to the loss of other RA responses of NIH 3T3 cells, including growth inhibition, retinoic acid catabolism, down-regulation of fibronectin biosynthesis, and induction of tissue-type transglutaminase, which are not seen to the same extent in NIH Ha-ras-3T3 cells.

3T3 Cells↗

PubMed1997

Retinoic acid inhibition of cell cycle progression in MCF-7 human breast cancer cells.

Cell cycle analysis indicates that retinoic acid (RA) inhibition of MCF-7 cell growth occurs through induction of G1 arrest with a concomitant reduction in the proportion of cells in S and G2 + M phases. RA did not affect cyclins D1, A, and E and cyclin-dependent kinase 2 (CDK2) expression, but significantly reduced cyclin D3 and CDK4 expression after 24 h. RA also inhibited cyclin B1 and CDC2 expression, possibly responsible for the reduction of the proportion of cells in G2 + M and S phases. RA did not induce p16 and p27 expression, but obviously reduced p21 level in MCF-7 cells. The retinoid markedly reduced pRB protein level and abrogated pRB phosphorylation after 48 h; it also reduced transcription factor E2F1 expression at both the mRNA and protein levels. E2F1 promoter activity was reduced by 60%, which is probably responsible, at least in part, for the reduction of E2F1 expression in RA-treated MCF-7 cells. These observations demonstrate a marked effect of RA on some of the key cell cycle regulatory proteins in MCF-7 cells. Cyclin D3 and CDK4 are likely the early targets of RA, followed by reduced pRB expression and phosphorylation, as well as by the inhibition of the E2F1 transcription factor which controls progression from G1 to S phase. Most of these events precede the observed reduction in MCF-7 cell growth, which begins at Day 3 of RA treatment.

Breast Neoplasms↗

PubMed1997

Aryl hydrocarbon receptor knockout mice (AHR-/-) exhibit liver retinoid accumulation and reduced retinoic acid metabolism.

Livers from aryl hydrocarbon receptor-null mice showed a 3-fold increase in retinoids and a 65% decrease in retinoic acid metabolism. Levels of expression of the retinoic acid 4-hydroxylase, P450RAI, did not change, whereas cytochrome P4501A2 levels were lower in the null mouse, as shown earlier; however, this enzyme was found not to be active toward retinoic acid. These data suggest that aryl hydrocarbon receptor controls retinoic acid catabolism, through modulation of an unidentified target gene. Aldehyde dehydrogenases 1 and 2 were down-regulated markedly in the aryl hydrocarbon receptor-deficient mouse liver. 2,3,7,8-Tetrachlorodibenzo-p-dioxin induced cytochrome P4501A2 but not the aldehyde dehydrogenases in wild-type mice, suggesting that aryl hydrocarbon receptor is not involved directly in the down-regulation of this gene. Transglutaminase II, a retinoic acid-responsive gene product, was increased 2-fold, consistent with the liver fibrosis phenotype observed in the null mice. These findings suggest a molecular connection between xenobiotic-activated receptor signaling and retinoid homeostasis.

Animals↗

PubMed1997

TPA induces transglutaminase C and inhibits cell growth in the colon carcinoma cell line SW620.

In contrast to most other systems, TPA induced TGc activity and protein in SW620 human colon carcinoma cells. This induction was accompanied by cell growth inhibition and increased apoptosis. The general protein kinase-C inhibitor GF-109203X blocked the induction of TGc by TPA, whereas the specific inhibitor of the PKC alpha isoform, the indocarbazole Go6976, reduced it by 40%. These PKC inhibitors had similar inhibitory effects on TPA increased apoptosis and inhibition of cell growth, suggesting that the observed actions of TPA are mediated by PKC, and a close connection between TGc activity, increased apoptosis and cell growth inhibition. We conclude that TPA may offer new approaches in the management of colon cancer cell growth.

Apoptosis↗

PubMed1997

Retinoic acid downregulates growth, fibronectin and RAR alpha in 3T3 cells: Ha-ras blocks this response and RA metabolism.

Retinoic acid (RA) reduced growth, fibronectin, and retinoic acid receptor (RAR alpha) in NIH 3T3 cells but not in cells transformed by the Ha-ras oncogene. RA lowered RAR alpha transcript and protein, increased RAR beta transcripts, and had no effect on RAR gamma. H-ras transformation downregulated RAR expression and abolished responsiveness to RA. Ha-ras-transformed cells were as active as normal NIH-3T3 cells in RA uptake but were unable to degrade it to medium oxidation product, so that, paradoxically, the resistant cells accumulated 20-30-fold as much RA as the sensitive cells. RA sensitivity/insensitivity correlated with RA metabolism/lack thereof in 15 cell lines in serum-free medium. These data suggest a relationship between RA inhibition of cell growth and intracellular RA metabolism.

3T3 Cells↗

PubMed1996

Loss of retinoic acid receptors in mouse skin and skin tumors is associated with activation of the ras(Ha) oncogene and high risk for premalignant progression.

Retinoic acid receptor transcripts (RARalpha and RARgamma) are decreased in benign mouse epidermal tumors relative to normal skin and are almost absent in carcinomas. In this report, the expression of RARalpha and RARgamma proteins was analyzed by immunoblotting in benign skin tumors induced by two different promotion protocols designed to yield tumors at low or high risk for malignant conversion. RARalpha was slightly reduced in papillomas promoted with 12-O-tetradecanoylphorbol-13-acetate (low risk) and markedly decreased or absent in papillomas promoted by mezerein (high risk). However, mezerein also caused substantial reduction of RARalpha in nontumorous skin. RARgamma was not detected in tumors from either protocol and was greatly reduced in skin treated by either promoter. Both RARalpha and RARgamma proteins were decreased in keratinocytes overexpressing an oncogenic v-ras(Ha) gene, and RARalpha was underexpressed in a benign keratinocyte cell line carrying a mutated c-ras(Ha) gene. Introduction of a recombinant RARalpha expression vector into benign keratinocyte tumor cells reduced the S-phase population and inhibited [3H]thymidine incorporation in response to retinoic acid. Furthermore, transactivation of B-RARE-tk-LUC by retinoic acid was markedly decreased in keratinocytes transduced with the v-ras(Ha) oncogene (v-ras(Ha)-keratinocytes). Blocking protein kinase C function in v-ras(Ha)-keratinocytes with bryostatin restored RARalpha protein to near normal levels, reflecting the involvement of protein kinase C in RARalpha regulation. Both RARalpha and RARgamma are down-regulated in cultured keratinocytes by 12-O-tetradecanoylphorbol-13-acetate, further implicating PKC in the regulation of retinoid receptors. Our data suggest that modulation of RARs could contribute to the neoplastic phenotype in mouse skin carcinogenesis and may be involved in the differential promoting activity of mezerein and 12-O-tetradecanoylphorbol-13-acetate, particularly for selecting tumors at high risk for malignant conversion.

Animals↗

PubMed1996

Regulation of cornifin alpha expression in the vaginal and uterine epithelium by estrogen and retinoic acid.

In this study, we analyze the regulation of the squamous-specific gene, cornifin alpha, by estrogen and retinoic acid in vaginal and uterine epithelial cells. In ovariectomized animals, the vaginal epithelium consists of a stratified, nonkeratinizing epithelium which changes into a highly-stratified, keratinizing epithelium upon treatment with estradiol. This transition is accompanied by a dramatic induction of the crosslinked envelope precursor, cornifin alpha. An increase in cornifin mRNA can be detected as early as 3 h after treatment. A similar effect is observed for the synthetic estrogenic agent diethylstilbestrol while other steroid hormones, including testosterone, progesterone or dexamethasone have little effect on cornifin expression. In contrast to the vagina, estradiol induces neither squamous differentiation nor expression of cornifin alpha in the uterine epithelium. Similar to the action of estradiol, vitamin A-deficiency greatly enhances squamous differentiation and keratinization in the vaginal epithelium. But unlike estradiol, it induces squamous metaplasia in the normally columnar, uterine epithelium, which eventually is replaced by a keratinizing epithelium in severe deficiency. This transition is associated with an induction of cornifin alpha expression. Immunohistochemical and in situ hybridization analysis localizes cornifin protein and mRNA in the suprabasal layers of the squamous epithelium. Our results demonstrate that estrogen and retinoids play key roles in the regulation of differentiation and cornifin alpha expression in the uterine and vaginal epithelium.

Animals↗

PubMed1996

Estrogen induces retinoid receptor expression in mouse cervical epithelia.

Steroid hormones and retinoids are powerful regulators of normal epithelial differentiation and function in the mouse female reproductive tract, where their actions are mediated by nuclear receptors. The expression pattern, heterodimeric interactions, and availability of ligand of these transcription factors are thought to contribute to the biological response. Estrogen (E2) induces proliferation and squamous differentiation of the cervical and vaginal epithelium during the mouse estrous cycle, while progesterone and retinoids maintain the simple columnar epithelium of the endocervix and uterine horns. We wanted to investigate whether retinoid receptors are responsive to estrogen status during cervical epithelial differentiation induced by a single dose of estrogen in ovariectomized adult mice. Northern blot analysis demonstrated a prolonged induction of RXR alpha and RAR gamma gene expression by E2 in the mouse cervix and vagina. When the induction of RXR alpha and RAR gamma was compared to genes known to be responsive to E2, including estrogen receptor (ER) and c-fos, RXR alpha was induced within 0.5 h of hormone treatment, while RAR gamma induction was evident by 4 h. The induction of these retinoid receptors suggests that they may be implicated in epithelial growth and differentiation in response to E2. Moreover, potential heterodimeric interactions among these receptors indicate that normal, cyclical epithelial differentiation results from the interplay of these molecules. Using in situ hybridization analysis, RXR alpha transcripts were localized preferentially in the basal cells, while ER mRNA was expressed throughout the epithelium of the ectocervix and vagina. Furthermore, ER transcripts were highly expressed in the stratified squamous foci induced by mild vitamin A depletion in the columnar epithelium of the endocervix and uterine horns. Therefore, the induction of RXR alpha and RAR gamma by E2 and their expression pattern in relation to ER suggest that they are needed to coordinate specific genetic programs that result in cervical epithelial growth and differentiation.

Animals↗

PubMed1996

Retinoic acid down-regulation of fibronectin and retinoic acid receptor alpha proteins in NIH-3T3 cells. Blocks of this response by ras transformation.

All-trans-retinoic acid (RA) markedly reduced the level of intracellular fibronectin (FN) in a time- and concentration-dependent fashion in NIH-3T3 cells, but not in NIH-3T3 cells transformed by an activated Ha-ras oncogene. Pulse/chase experiments indicated that RA affects FN biosynthesis rather than its turnover rate. Steady state levels of FN transcripts did not change after treatment of the cells with RA for various times or concentrations, suggesting that RA acts at the translational level. Similar effects were observed in other fibroblasts. In NIH-3T3 cells, RA had distinct effects on different receptors; it down-modulated retinoic acid receptor (RAR) a protein and transcript levels, it up-regulated RAR beta transcripts, and it had no effect on RAR gamma. Transformation of NIH-3T3 cells with an activated Ha-ras oncogene down-modulated RAR expression and abolished responsiveness to RA. We identified the retinoid signal transduction pathways responsible for the effects of RA on FN and RAR alpha proteins by the use of the retinoid X receptor-selective compound, SR11237, by stable over-expression of a truncated form of the RAR alpha gene, RAR alpha 403 with strong RAR dominant negative activity, and by overexpression of RAR alpha. We conclude that: 1) RA-dependent FN down-modulation is mediated by RARs, 2) retinoid X receptors mediate the observed reduction of RAR alpha by RA, and 3) the block of RA responsiveness in Ha-ras cells cannot be overcome by overexpression of RAR alpha. These studies have defined fibronectin and RAR alpha as targets of RA in fibroblast cells and have shown that oncogenic transformation renders the cells resistant to RA action.

3T3 Cells↗

PubMed1996

Dietary retinoic acid inhibits mouse skin carcinogenesis irrespective of age at initiation.

In the two-stage protocol of skin carcinogenesis, the carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) is applied to the skin of mice at around seven weeks of age. We previously performed DMBA initiation at three weeks of age to study the effect of pharmacological (30 micrograms/g diet) dietary retinoic acid (RA) on skin carcinogenesis. In this study we asked whether dietary pharmacological RA is equally effective against skin carcinogenesis when mice are initiated with (DMBA) at 7 weeks of age and then subjected to weekly applications of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) or mezerein (MEZ) for 20 weeks. Similar to the three-week initiation protocol, high dietary RA inhibited papilloma incidence and yield in MEZ- but not in TPA-promoted female SENCAR mice. In addition, carcinoma incidence and yield were decreased by high dietary RA in TPA- as well as MEZ-treated mice. These data demonstrate that the high dietary RA diet is as effective in inhibiting papilloma and carcinoma formation when the DMBA is applied at seven weeks of age as at three weeks.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1996

A new metabolite of retinol: all-trans-4-oxo-retinol as a receptor activator and differentiation agent.

All-trans-4-oxo-retinol, a metabolite of retinol synthesized in mouse embryonal carcinoma F9 cells, is active in inducing differentiation of these cells. It also functions as a ligand of retinoic acid receptors and a transcriptional activator of reporter genes. These findings may dispel the notion that retinoic acids are the only transactivators of retinoid receptor-dependent pathways. However, there are weaknesses that need to be addressed in order to confirm the relevance of this retinol-mediated signaling pathway.

Animals↗

PubMed1996

Retinoic acid response elements as positive and negative regulators of the expression of the homeobox b-1 gene.

Retinoic acid-dependent homeobox Hoxb-1 gene expression offers an unanticipated example of both a positive and a negative transcriptional activity of RA, as exerted at different times during embryogenesis. A paradigm for the transduction of positive and negative signaling is the discovery that retinoic acid response elements (RAREs), positioned in the 3' enhancer and 5' promoter of the Hoxb-1 gene, may function respectively as positive and negative regulators, thereby permitting a diffused (early positive) as well as segmentally specified and limited (late negative) expression of the gene. This molecular action of retinoic acid may provide a mechanism for our understanding of normal embryogenesis and of the interference with this process by ectopic retinoic acid, thereby leading to teratogenesis.

Abnormalities, Drug-Induced↗

PubMed1996

Beta-carotene increases lung cancer incidence in cigarette smokers.

Clinical trials were designed to validate the protective effect of beta-carotene in populations of cigarette smokers at high risk for lung cancer development. Strikingly, an increase in lung cancer resulted following beta-carotene supplementation in two separate studies in Finland and the United States. These trials were conducted without any evidence that beta-carotene prevents lung cancer in animal models.

Aged↗

PubMed1996

Selective changes in laminin adhesion and alpha 6 beta 4 integrin regulation are associated with the initial steps in keratinocyte maturation.

In skin, the distribution of integrins is compartmentalized. Whereas the alpha 6 beta 4 integrin complex is polarized to the basal portion of proliferating cells in the basal layer juxtaposed to the basement membrane, alpha 3 beta 1 integrin receptors are localized on the cell surface surrounding basal and suprabasal cells, suggesting beta 1 integrins mediate both cell-matrix and cell-cell interactions. As initiation of maturation in skin is associated with the detachment of cells from the basement membrane, the early loss of alpha 6 beta 4, but not alpha 3 beta 1, integrin expression could be a determining factor in the transition from the proliferating to a differentiating keratinocyte. We have studied the regulation of adhesion potential and integrin expression during differentiation of mouse basal keratinocytes culture in 0.05 mM Ca2+ medium and induced to differentiate in 0.12 mM Ca2+ medium. Within 12-24 h after elevation of Ca2+, a selective loss of the alpha 6 beta 4 integrin complex is associated with the induction of the spinous cell marker keratin 1. This early differentiation phenotype coincides with loss of cell attachment mediated by alpha 6 beta 4 to laminins 1 and 5 but not a fibronectin or collagen IV. Selective loss of attachment to laminin is also detected in spinous cells isolated from newborn epidermis in vivo. The loss of alpha 6 and beta 4 protein expression is a consequence of transcriptional and posttranscriptional events, including reduction in mRNA transcripts, reduced synthesis of the alpha 6 protein, and enhanced processing of the alpha 6 and beta 4 chains as determined by Western blots and pulse-chase experiments in metabolically labeled keratinocytes. Selective processing of the beta 4 intracellular domain is detected before loss of beta 4 from the cell surface in basal keratinocytes, and this process is accelerated during differentiation. Whereas early keratinocyte maturation is linked to the selective loss of the alpha 6 beta 4 complex, loss of both beta 1 and beta 4 integrin mRNA and protein occurs as cells proceed to later stages in the differentiation program as induced by 0.5 mM Ca2+ or suspension culture. These conditions are characterized by accelerated expression of transglutaminase; reduced keratin 1 protein; loss of adhesion to fibronectin, laminin 1, laminin 5, and collagen IV; and rapid cell death. Contributing to the down-regulation of beta 1 integrins during terminal differentiation is a selective sensitivity of alpha 3 beta 1 but not alpha 6 beta 4 to down-regulation by transforming growth factors beta 1 and beta 2, factors that are also expressed differentially in normal skin. This study indicates that down-regulation of the alpha 6 beta 4 but not beta 1 integrins occurs during the initial steps of keratinocyte differentiation and is associated with detachment from the laminin matrix. Such changes could contribute an important signal to initiate the process of terminal keratinocyte differentiation.

Animals↗